Vehicle engines may be configured to shut-off during idle conditions when the vehicle comes to a stop while a brake is applied and restarted once the brake is released (e.g., a stop/start system) in order to reduce fuel consumption. Fuel consumption may be further reduced by shutting down the engine during braking or by shutting down the engine when the operator is not braking and not requesting torque, before the vehicle has come to a stop.
One approach to shutdown and subsequently restart the engine while the vehicle is traveling is disclosed in U.S. Pat. No. 6,951,525. In the cited reference, the engine is restarted prior to a transition from free-wheel mode to engaged clutch travel mode by employing the fuel injection system using a charge regulator and/or an electric motor. In one embodiment the charge regulator reactivates the engine by sequentially activating a fuel injection system. In an alternative embodiment, engine restart may be supported by an electric motor. After the engine is restarted, the reference describes using a throttle to bring the engine speed closer to the speed of the transmission before a transmission clutch is engaged. However, it may take more time than is desired to bring the speed of the engine close to the speed of the transmission, and as a result, the clutch engagement may be delayed. On the other hand, if the clutch is engaged before the engine speed is close to the transmission speed, clutch degradation may increase.
The inventors herein have recognized the above problems and have devised an approach to at least partially address them. Thus, a method for controlling an engine coupled to a transmission in a vehicle is disclosed. A method for controlling a vehicle engine, the engine being coupled to a transmission, comprising: in response to a first operating condition, restarting the engine by at least partially engaging the transmission to assist in spinning-up of the engine from rest while the vehicle is traveling; and adjusting at least one of a throttle position, spark advance, cam angle, and fuel timing in response to a second operating condition.
Thus, in one example embodiment, an engine is restarted by engaging the transmission and positioning the engine controls when the engine is at rest. For example, while the vehicle is moving, the wheel torque can be supplied to the engine by engaging a clutch between the engine and the transmission. Further, engine controls can be adjusted during the start to limit engine torque during the start. Adjusting the engine controls at engine start can reduce vehicle surge and lower the amount of clutch slippage that provides a smooth the transition between non-combusting and combusting engine modes. In this way, the transmission and engine are controlled so that the engine is quickly started and so that the operator experiences less torque at engine restart.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.